Benefits for pastures and crops
Planted shelter belts slow down the wind. This reduces moisture loss from soil and plants in summer and autumn, and helps delay the effects of drought. It limits buffeting of fruit, shoots and flowers by strong wind, and makes it easier for insects to pollinate plants.
It’s an ill wind
The large number of shelter belts in Canterbury were mostly planted against the South Island’s famous nor’wester wind, which blows across the Canterbury Plains from the Southern Alps. The westerly airstream rises over the mountains, increasing in speed as it descends onto the eastern plains. The dry land warms the wind in summer and autumn, so it is often strong, dry and hot, and can cause soil erosion.
Depending on crop type, soil moisture levels, rainfall and wind speed, sheltered crops may produce 5–15% more than those without shelter. Shelter belts around orchards also help reduce drift of horticultural sprays to about 12% of that from unsheltered areas.
Shelter can also reduce soil erosion by wind.
Benefits for animals
Shelter is generally beneficial to livestock. Animals gather in shade during hot weather, and take refuge from cold winds. Sheltered animals need less feed to maintain physical condition, and their winter growth rates improve. Sheep and cattle can comfortably withstand lower temperatures than humans, because they generate internal heat through biological activity in the rumen (first compartment of the stomach), as long as they are well fed.
The domestic animals most vulnerable to hypothermia are newborn lambs and recently shorn sheep – but these are more likely to seek shelter than older lambs or woolly ewes. Shelter has been shown to reduce spontaneous abortions and lamb losses from hypothermia. Ewes prefer to lamb in isolation from the flock and will seek out shelter to do this if it is available.
Cattle are less susceptible than sheep to hypothermia in cold weather. But shelter from the sun during hot weather can improve milk production and conception rates in dairy cows, and the growth rate in fattening cattle.
Deer benefit from reduced wind speed in cold conditions, and shade in hot weather. They also use shelter to hide their fawns and to provide secluded mating sites. Trees in a paddock have a calming effect on deer, reducing their tendency to run along fencelines and create tracks that become eroded.
Dogs also need good shelter. In order to rest adequately and stay healthy, they should have water- and wind-proof kennels which are kept clean and dry.
Other benefits of shelter
In serious droughts, the foliage from shelter belts (such as poplar and willow species) can be harvested and used to feed stock. Use of appropriate tree species may encourage bees, especially in early spring, and predators or parasites of crop pests. Shelter belts also provide habitats for birds, and native trees may attract native birds.